- add ability to provide an empty string in case the regex does not match

- FIX https://github.com/mikepenz/release-changelog-builder-action/issues/576

__tests__/transform.test.ts

@@ -18,6 +18,10 @@ configuration.categories = [
   {
     title: '## 🧪 Tests',
     labels: ['[Test]']
+  },
+  {
+    title: '## 🧪 Others',
+    labels: ['[Other]']
   }
 ]
 
@@ -192,6 +196,31 @@ it('Extract label from title, match multiple', async () => {
   )
 })
 
+it('Extract label from title, match multiple, custon non matching label', async () => {
+  configuration.label_extractor = [
+    {
+      pattern: '\\[Feature\\]|\\[Issue\\]',
+      on_property: 'title',
+      method: 'match',
+      on_empty: '[Other]'
+    }
+  ]
+
+  const resultChangelog = buildChangelog(mergedPullRequests, {
+    owner: 'mikepenz',
+    repo: 'test-repo',
+    fromTag: '1.0.0',
+    toTag: '2.0.0',
+    failOnError: false,
+    commitMode: false,
+    configuration
+  })
+
+  expect(resultChangelog).toStrictEqual(
+    `## 🚀 Features\n\n- [Feature][AB-1234] - this is a PR 1 title message\n   - PR: #1\n- [Issue][Feature][AB-1234321] - this is a PR 3 title message\n   - PR: #3\n\n## 🐛 Fixes\n\n- [Issue][AB-4321] - this is a PR 2 title message\n   - PR: #2\n- [Issue][Feature][AB-1234321] - this is a PR 3 title message\n   - PR: #3\n\n## 🧪 Others\n\n- [AB-404] - not found label\n   - PR: #4\n\n`
+  )
+})
+
 // test set of PRs with lables predefined
 const pullRequestsWithLabels: PullRequestInfo[] = []
 pullRequestsWithLabels.push(

src/configuration.ts

@@ -34,6 +34,7 @@ export interface Transformer extends Regex {
 export interface Extractor extends Transformer {
   on_property?: 'title' | 'author' | 'milestone' | 'body' | undefined // retrieve the property to extract the value from
   method?: 'replace' | 'match' | undefined // the method to use to extract the value, `match` will not use the `target` property
+  on_empty?: string | undefined // in case the regex results in an empty string, this value is gonna be used instead (only for label_extractor currently)
 }
 
 export interface TagResolver {

src/transform.ts

@@ -302,9 +302,11 @@ export function validateTransformer(
   try {
     let onProperty = undefined
     let method = undefined
+    let onEmpty = undefined
     if (transformer.hasOwnProperty('on_property')) {
       onProperty = (transformer as Extractor).on_property
       method = (transformer as Extractor).method
+      onEmpty = (transformer as Extractor).on_empty
     }
 
     return {
@@ -314,7 +316,8 @@ export function validateTransformer(
       ),
       target: transformer.target || '',
       onProperty,
-      method
+      method,
+      onEmpty
     }
   } catch (e) {
     core.warning(`⚠️ Bad replacer regex: ${transformer.pattern}`)
@@ -347,7 +350,7 @@ function extractValues(
 
   if (extractor.method === 'match') {
     const lables = onValue.match(extractor.pattern)
-    if (lables !== null) {
+    if (lables !== null && lables.length > 0) {
       return lables.map(label => label.toLocaleLowerCase('en'))
     }
   } else {
@@ -356,6 +359,9 @@ function extractValues(
       return [label.toLocaleLowerCase('en')]
     }
   }
+  if (extractor.onEmpty !== undefined) {
+    return [extractor.onEmpty.toLocaleLowerCase('en')]
+  }
   return null
 }
 
@@ -364,4 +370,5 @@ export interface RegexTransformer {
   target: string
   onProperty?: 'title' | 'author' | 'milestone' | 'body' | undefined
   method?: 'replace' | 'match' | undefined
+  onEmpty?: string | undefined
 }